Connecting rod of an internal combustion engine for changing the compression ratio

ABSTRACT

The connecting rod head includes at least one oil chamber and an eccentric comprises a protrusion reaching into the oil chamber, so that an oil pressure in the oil chamber exerts a force on the protrusion to change the eccentric setting of the eccentric.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from Application 102019115994.6 filedon Jun. 12, 2019 in Germany; 102019103998.3 filed on Feb. 18, 2019 inGermany; 102018119709.8 filed on Aug. 14, 2018 in Germany; and102018115484.4 filed on Jun. 27, 2018 in Germany.

FIELD OF THE INVENTION

The present disclosure relates to a connecting rod for an internalcombustion engine with a variable compression ratio.

BACKGROUND OF THE INVENTION

Internal combustion engines with a variable compression ratio are knownfor example from WO 2014/019683 A1. In the device disclosed there, aneccentric is used to adjust an optimized compression ratio depending onthe given combustion conditions. In this device, two hydraulic cylindersare used, also known as support cylinders, with which the eccentric(ring) can be turned relative to the head of the connecting rod, bywhich the compression ratio is changed.

In engines with a large stroke/bore ratio (s/D≥1.3), the supportcylinders require a relatively large design space, with the result thatthe space in the engine cylinder for the corresponding connecting rodbecomes quite tight. The space also becomes tight in the case of a largedisplacement for the connecting rod, since it performs not only areciprocating movement, but also a swiveling movement.

The problem which the present disclosure proposes to solve is to providean alternative device for adjusting the compression ratio. Inparticular, a space-saving design is desired, so that high stroke/boreratios, as well as piston pin to bore ratios can be realized. Moreover,the overall weight of the device for switching the compression ratioshould be as low as possible.

SUMMARY

A connecting rod for an internal combustion engine includes a device forchanging a compression ratio (VCR), having a connecting rod head and aconnecting rod pin, which is mounted by an eccentric relative to theconnecting rod head. The connecting rod head or the connecting rod pinincludes at least one oil chamber and the eccentric includes aprotrusion reaching into the oil chamber, so that an oil pressure in theoil chamber exerts a force on the protrusion to change the eccentricsetting of the eccentric. The oil chamber is bounded by a radial surfaceof the eccentric, among others. The protrusion in particular is radial,or it has a radial component of its orientation. The eccentric inparticular is ring-shaped with round non-coaxial outer and inner lateralsurfaces. The protrusion in particular is a single piece with theeccentric or rigidly joined to it. The connecting rod pin may also beviewed as being a section of the crankshaft. The oil chamber may beviewed as being a curved hydraulic cylinder, which is situated aroundthe eccentric and in which the protrusion is received. Thus, traditionalhydraulic cylinders are no longer needed. Furthermore, with such an oilchamber a swiveling movement of the eccentric in both directions can beachieved. This saves on design space. If, furthermore, multiple oilchambers are used, they can be correspondingly smaller in design toachieve the same setting torque. Moreover, multiple oil chambers havethe benefit of less risk of canting when the swivel forces aregenerated. The protrusions may alternatively be directed radiallyinward, so that the oil chamber(s) in this case is/are arranged on theconnecting rod pin. It is furthermore seen as being equivalent for theeccentric to comprise an oil chamber and for the protrusion to be on theother respective functional part. In other words: the oil chamber mayhave a defined movement range for the protrusion, at the ends of whichis situated respectively at least one oil inlet and one oil outlet. Inthis way, a dual-action device is provided, which is space-saving. Themovement range can be limited by end stops at both ends.

Moreover, it is advantageous for a lubricant supply chamber to beprovided between the connecting rod head and the eccentric and for theeccentric to have a breach associated with the lubricant supply chamber.Thus, regardless of the set eccentric angle a fluidic connection isalways created between a supply duct of the connecting rod and a supplyduct of the connecting rod pin. It is possible to provide a lubricantsupply chamber whose circumferential extension substantially correspondsto the setting angle range for changing the eccentric setting and bywhich a fluidic connection exists between the connecting rod head andthe connecting rod pin in every position of the eccentric. Here, theterm “substantially” means embodiments in which no structural featuresare provided which hinder or impede an identical design of the angleranges. And/or the angle ranges may differ from each other by as much as+/−10°. The circumferential extension describes an angle range about thecenter point of the eccentric.

In particular, a lubricant supply chamber or the lubricant supplychamber is provided in a plane in which the oil chamber is alsoprovided. Thus, the oil chamber may extend over the entire width of theconnecting rod (i.e., in the axial direction of the connecting rodbearing) and thus bring about large forces. Alternatively, a lubricantsupply chamber may be provided in a plane in which the oil chamber isnot situated. In particular, the lubricant supply chamber may then beconfigured, for example, as a (partially) encircling groove. In thiscase, the transfer of the lubricant from the connecting rod to thepiston is carried out in laterally offset fashion in the longitudinaldirection of the piston pin. In this way, more oil chambers can beprovided for the torque transmission.

In another embodiment, the connecting rod head includes at least two oilchambers, each one having a protrusion. The connecting rod head mayinclude exactly two oil chambers, each one having the protrusion. Themore oil chambers of this kind are used, the better the torque can betransmitted to the eccentric, although space limits restrict the numberof oil chambers and/or their angle range.

Moreover it is advantageous for the connecting rod head to comprise alocking, which is hydraulically or mechanically actuable, and which canbe brought into a state of locking which prevents a relative movement ofthe connecting rod head and the eccentric or a relative movement of theeccentric and the connecting rod pin. The locking may be form fitting.Thanks to the locking it can be ensured that the eccentric alwaysremains in its nominal position, even under pressure fluctuations in theeccentric switching system.

In particular, the oil chamber or oil chambers include an oil inlet andan oil outlet at opposite ends in order to realize a first compressionratio, whose functions can be exchanged in order to realize a secondcompression ratio. This creates a dual action of the hydraulic system.

Moreover, the eccentric may be adjustable in an angle range of more than40°, in some cases at least 90° relative to the connecting rod head.This angle range may also be less than 160°. A large angle range ishelpful in accomplishing the eccentric action.

A connecting rod with a device for changing a compression ratio (VCR)for an internal combustion engine may include a connecting rod head anda connecting rod pin, which is mounted by an eccentric relative to theconnecting rod head. A releasable locking can be provided here in atleast one switching position, wherein the locking in a locking positionprevents in particular a rotating of the eccentric relative to theconnecting rod head. The eccentric can be placed in at least twodifferent positions relative to the connecting rod head. The connectingrod head is preferably formed by an axial end of the connecting rod. Theconnecting rod head considered here can be located at the end of theconnecting rod which is distant from the crankshaft. In this case, theconnecting rod pin supports the piston of the engine. Alternatively, theVCR adjustment may be at the end of the connecting rod which is close tothe crankshaft. In this case, the connecting rod pin is part of thecrankshaft. The combination of the connecting rod with the connectingrod pin can also be called a connecting rod assembly. The at least oneswitching position is associated each time with one compression ratio.Preferably, there are at least two and in particular precisely twodefined switching positions. By protruding means, a detent in thedesired switching position is realized. This brings the advantage thatthe desired ratio is always set and remains set in a permanent andreproducible manner. Furthermore, it has been found that this design cansignificantly reduce the wear and significantly increase the fatiguestrength, because in known designs not using a corresponding lockingthere is always a certain slippage present, or a relative movement fromthe eccentric to the adjacent components. This places a strain on thesealing elements and/or corresponding cylinders of the switchingprocess. By preventing these relative movements, there is practically nostrain on the sealing and bearing components, among others, used in thecondition of no switching of the compression ratio.

It is advantageous for a releasable locking to be provided in each casein at least two switching positions. Especially at the highercompression ratio, large forces are exerted on the mechanism andhydraulic assembly, so that there are special benefits here for alocking. On the other hand, it has also been found that these benefitsmay be used for both switching positions.

In particular, the locking may comprise a pin, which can engage with aseat, and a hydraulic drive is provided in particular for this. This isone exemplary embodiment. Other embodiments such as hooks engaging by asliding surface or clamps can be used in an understanding of theequivalence for the locking.

It is moreover preferable for a drain from the hydraulic system of theconnecting rod, the drain having a relief throttle, to be provided, bywhich system hydraulic fluid can be supplied to the engine interiorafter the activation of a switching actuator for the switching process.In particular in this case, the throttle may also be designed as a ductwith a reduced cross section and in particular the reduced cross sectionof this duct is less than 25% of the duct for the supply of thehydraulic fluid for the compression change. In this way, a pressurerelief is created for the locking of the switching device. It is alsopossible to provide a drain from the hydraulic system of the connectingrod, the drain having a throttle, by which drain hydraulic fluid can besupplied to the engine interior after the activation of a switchingactuator for the switching process, and to arrange the throttle in avalve, especially the switching actuator, wherein in particular thethrottle can be designed as a leakage of a valve.

In some embodiments, there is no hydraulic fluid supplied via thethrottle to the engine interior in the time span after performing aswitching of the compression ratio until a new activation of theswitching actuator occurs. Thus, hydraulic fluid does not need to besupplied continuously to the connecting rod.

In some embodiments, a device for changing a compression ratio for aninternal combustion engine may include a connecting rod head and aconnecting rod pin, which is mounted by an eccentric relative to theconnecting rod head, wherein two end positions are provided for theadjustability of the eccentric and a dampening is provided for at leastone end position in that a component, such as a protrusion of theeccentric, reduces a flow channel for a hydraulic fluid inposition-dependent manner, in order to thereby reduce the velocity ofthe eccentric during the movement into an end position. When switchingthe compression ratio, the hydraulic fluid flows out of (or into) acorresponding volume and for the greater portion of the movement path ofthe eccentric its flow resistance remains constant. Near the endpositions, the flow resistance increases on account of the reduction ofthe flow duct, which brakes the speed of movement of the eccentric andthus prevents a hard impact against an end stop.

In a further aspect, a connecting rod may be outfitted with a device forchanging a compression ratio (VCR) for an internal combustion engine andcomprise two bearing regions, on the one hand for mounting theconnecting rod relative to a piston, and on the other hand for mountingon a crankshaft of the internal combustion engine. A switching actuatorfor activating the adjustment of the compression ratio is in this casearranged between the two bearing regions. In this way, the flow pathsand duct lengths inside the connecting rod are shortened, whichincreases the response speed and lowers the manufacturing costs.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the embodiments shall be explained as an example withthe aid of the drawings. There are shown:

FIG. 1 schematically depicts a perspective view of a connecting rodaccording to one or more embodiments described and illustrated herein;

FIG. 2 schematically depicts an exploded view of an upper part of theconnecting rod of FIG. 1 according to one or more embodiments describedand illustrated herein;

FIG. 3 schematically depicts a central section through the head of theconnecting rod according to one or more embodiments described andillustrated herein;

FIG. 4 schematically depicts a section through the head of theconnecting rod in plane A-A of FIG. 7 according to one or moreembodiments described and illustrated herein;

FIG. 5 schematically depicts a section through the head of theconnecting rod in plane B-B of FIG. 7 according to one or moreembodiments described and illustrated herein;

FIG. 6 schematically depicts a detail A of FIG. 4 according to one ormore embodiments described and illustrated herein;

FIG. 7 schematically depicts a longitudinal section through theconnecting rod with the connecting rod pin 50 according to one or moreembodiments described and illustrated herein;

FIG. 8 schematically depicts an alternative embodiment of the adjustingdevice for the eccentric 40 according to one or more embodimentsdescribed and illustrated herein;

FIG. 9 schematically depicts a circuit diagram of the hydraulic systemwithin the connecting rod according to one or more embodiments describedand illustrated herein;

FIG. 10 schematically depicts section A-A of FIG. 7 according to one ormore embodiments described and illustrated herein;

FIG. 11 schematically depicts an enlarged feature of the connecting rodin the area of the hydraulic lines according to one or more embodimentsdescribed and illustrated herein;

FIG. 12 schematically depicts an embodiment of a connecting rod with afurther alternative releasable locking according to one or moreembodiments described and illustrated herein;

FIG. 13 schematically depicts a section through the embodiment shown inFIG. 12 according to one or more embodiments described and illustratedherein;

FIG. 14 schematically depicts an embodiment of a connecting rod with afurther alternative releasable locking according to one or moreembodiments described and illustrated herein;

FIG. 15 schematically depicts a section through the embodiment shown inFIG. 14 in a locked first switching position according to one or moreembodiments described and illustrated herein; and

FIG. 16 schematically depicts a section through the embodiment shown inFIG. 14 in a locked second switching position according to one or moreembodiments described and illustrated herein.

DETAILED DESCRIPTION

FIG. 1 shows in perspective view a connecting rod for a VCR (variablecompression ratio) switching system, in which the engine can havedifferent compression ratios. At the right is shown a bearing region ofthe connecting rod, by which it is mounted on the crankshaft. And aswitching actuator 31 can be seen. In the engine housing there arearranged deflector plates, which can be moved in the longitudinaldirection of the crankshaft and when these deflector plates areactivated the switching actuator 31 is displaced. Via the crankshaft theconnecting rod is supplied with lubricating oil, which at first servesfor lubricating the bearings of the connecting rod and the piston andfor its cooling. A portion of this oil is taken to the switchingactuator 31, which comprises a hydraulic valve (not shown) and conductsthe lubricating oil into corresponding ducts of the connecting roddepending on the switching state, which has the end effect of switchingthe compression ratio.

In FIGS. 2 and 3 an eccentric (ring) 40 can be seen, which is rotatablymounted in the connecting rod head 20 and which in turn supports aconnecting rod pin 50 (see FIG. 7), which in turn supports a piston 70.When the eccentric 40 is turned in the plane of the drawing of FIG. 3,the position of the connecting rod pin 50 is displaced in thelongitudinal direction of the connecting rod 20.

As a guide element for the eccentric 40, it is provided with aprotrusion 42 respectively at two radially outside points, which reachinto oil chambers 25. The oil chambers 25 are arranged in the form of aring-shaped arc section in the connecting rod head 20 and are providedat their ends respectively with an oil inlet 16 and an oil outlet 18,which act in opposition for the oppositely directed eccentric movement.The cross section of the oil chambers 25 is sealed fluid-tight by theprotrusion 42, making use of sealing elements 44. When the switchingactuator 31 is placed in the position shown in FIG. 9, oil flows intothe inlet 16 and at the same time an outflow through the outlet 18 ismade possible. A rotary movement of the eccentric 40 can now occur,which is basically accomplished by forces arising in the combustion andacting on the eccentric via the piston. Oil flowing in at the oil inlet16 supports this movement. A check valve 76 ensures that the eccentric40 in this switching state cannot move in the respectively oppositelydirected movement. Furthermore, this movement is also supported by theinertial forces (mass forces) of the connecting rod and the eccentric. Aswitching of the switching actuator 31 brings about a reversal of theoil flows and a reversal of the eccentric 40 in the other direction. Atthe end points of this a rotational range thus produced with the anglerange a there is provided a respective end stop 22. The oil flow, asalready explained, is initiated by the switching actuator 31. The devicerequired for this is arranged in the lower part of the connecting rod10, i.e., at the crankshaft side. In FIG. 10, for example, acorresponding hydraulic guide is shown within the connecting rod head20. Bores are employed for this, being closed at the connecting rodoutside, and this is supplemented by a duct closed by a covering 29. Bythese means, the oil is conveyed to the transfer points into the oilchambers 25, which may respectively act as oil inlets 16 or oil outlets18. A corresponding hydraulic guide is provided for the transfer point18. This is offset transversely to the connecting rod longitudinaldirection as compared to the hydraulic guide shown in FIG. 10. In someembodiments, at least one oil chamber 25 is required, while preferablymore than 2, namely 3 or more oil chambers, can also be used.

FIGS. 3 and 7 show an oil supply duct 27, which serves for the supplyingof oil for lubricating and cooling purposes and is oriented in thelongitudinal direction in the connecting rod 10, emerging into alubricant supply chamber 26. The lubricant supply chamber 26 isassociated with a breach 46 of the eccentric 40. And the lubricantsupply chamber 26 has a circumferential extension, corresponding to theangle range a for the adjustability of the eccentric and is arrangedsuch that oil can flow into the eccentric 40, namely, a supply duct 57situated there (see FIG. 7), at each angle setting of the eccentric 40.The oil is taken via further pin ducts 52 to the piston 70, where theoil performs its lubricating and cooling functions. The flow directionis indicated by small arrows in FIG. 7.

FIGS. 4 and 5 show in sectional view together with the detail of FIG. 6a locking device 60, which can be initiated each time by one of the oilflows for switching of the compression ratio. The cross sections shownA-A and B-B run transversely and off-center through the connecting rod10, as is seen from FIG. 7. According to FIG. 6, the locking device 60comprises a detent piston 62, which is mounted in the connecting rodhead 20 and has an end which can be received in a seat 65 of theeccentric 40. A spring 64 presses the detent piston 62 in this directionand a hydraulic chamber of the detent piston 62 is arranged such thatcorresponding oil pressure can overcome the spring force of the spring64 and can thus pull the detent piston 62 out from its seat 65. Thisdesign can ensure that even under certain pressure fluctuations withinthe oil supply system for the oil inlets and oil outlets 16 and 18 theeccentric 40 constantly remains in its nominal position, as long as nodemand for switching is present. Also during every crankshaft revolutionthere exists a relative movement between the piston 70 and theconnecting rod 10 and the bearing position of this relative movement isdefined by the locking device 60, which comprises a detent piston 62 anda spring 64. It is ensured that, in the locking state, no relativemovement of the eccentric 40 and the connecting rod head 20 can occur.The two locking systems are situated at the end points of the adjustablerange of the eccentric 40. At the location at which the breach 46 isshown in FIG. 3, the seat for the detent piston 62 is arranged in thethickness direction of the connecting rod 10 (i.e., perpendicular to theplane of the drawing of FIG. 3). Accordingly, FIG. 3 shows the positionof the eccentric 40 in which the detent piston of FIG. 5 can be receivedin its seat. A further seat is arranged in a position which is in thelongitudinal direction of the connecting rod pin to the aforementionedseat, in which the detent piston 62 of FIG. 4 can be received. Thedetent pistons thus lie in the planes A-A and B-B of FIG. 7.

FIG. 8 shows as an example two alternative embodiments which may be usedindependently of each other. Firstly, two hydraulic cylinders 80 areshown with corresponding pistons, which are configured as a lineardrive. In this embodiment, the above described oil chambers 25 with thecorresponding protrusions 42 are not used. Instead, the hydrauliccylinders are coupled by a corresponding mechanism, such as a web 49, tothe eccentric 40. If, optionally, one or the other of the hydrauliccylinders 80 is extended by application of pressure, the eccentric 40will rotate accordingly relative to the connecting rod head 20.Furthermore, a switching actuator 31′ of an alternative embodiment isshown. As described above and depicted in FIG. 1, a switching actuator31 can be on the “bottom” i.e., at that end of the connecting rod whichis distant from the piston 70. The already described deflector platescan be moved in the crankshaft longitudinal direction and activate theswitching actuator, which projects beyond the connecting rod at one end,depending on the switching state. The switching actuator 31′ is arrangedadjacent to the eccentric 40. Thus, no duct system is needed extendingacross the connecting rod along its longitudinal direction, but insteadit can be connected by shorter connecting ducts to the hydrauliccylinders 80 or the oil chambers 25 and/or the locking system 60.

FIG. 9 shows an exemplary circuit diagram of the hydraulic system. Firstof all, it is shown how the connecting rod 10 is supplied with oil fromthe engine oil circuit. This occurs via the crankshaft and a fillingcheck valve 77, which only allows for the filling of the hydraulicsystem, but not a return flow into the engine oil circuit. In the flowdirection upstream from the filling check valve 77 there may be provideda branching (not shown), where oil is diverted for the lubricating ofthe connecting rod bearing. When the switching actuator 31 is switchedinto its position as shown here, oil flows on account of the forcesacting on the piston from the oil outlet 18 to the oil inlet 16. A backflow under a change in the force conditions is prevented by the checkvalve 76. At the same time, the locking system B2 is supplied withpressure, whereby the detent piston 62 is pulled out from the seat ofthe eccentric 40 against the spring force of the spring 64, so that theeccentric 40 is able to rotate. In other words, the unlocking must firstoccur by means of engine oil pressure. Only then is the eccentric ableto rotate. Only by the rotation of the eccentric are the pressurescreated which allow the oil to flow from 18 to 16.

The rotation of the eccentric 40 is brought about by the inflowing oil,connected with the forces of rotary/swiveling movement of the piston 70.In order to further assist and direct this movement, a further checkvalve 76 is provided in this oil flow. This prevents a backflow into therespective oil chamber 25 to be emptied or the piston 80. Thanks to theswitching of the switching actuator 31 to the indicated position, theeccentric 40 ends up in the other end position, not shown in FIG. 3.This has the result that the region in the flow direction downstreamfrom the check valve 76 becomes pressurized. The region in the flowdirection upstream from the check valve 76 is connected to the engineinterior via a relief throttle 75. In this way, a portion of thehydraulic fluid can be diverted from the hydraulic system. Thus, on theone hand, the pressure declines in this region and oil can thereby flowout from the hydraulic locking system 60. As a result, the equilibriumof forces in the locking system 60 is shifted, so that forces are builtup by the spring 64, which press the detent piston 62 against theeccentric 40. And as soon as the rotation of the eccentric aligns itscorresponding seat 65 with the detent piston 62, it is displaced intothe seat 65, which results in the locking in the switching position andthe switching process is terminated with this. For the switching to theother compression ratio, corresponding to the eccentric setting of FIG.3, the processes run accordingly, as can be directly seen from thecircuit diagram.

In the fluid direction upstream from the oil inlet 16, 18 there isarranged a respective throttle, which is termed in particular fillingthrottle 78 and which is situated behind a branch leading to therespective locking system B1, B2. These filling throttles 78 have thepurpose that, at the beginning of a switching process when the pressurein the respective system is rising, a sufficient fluid flow getsdirectly into the respective locking system B1 or B2, so that thislocking system B1, B2 is already released as fast as possible and thusthe adjustment process is quickly initiated, since only after thereleasing of the respective locking system can fluid get from the regionto be emptied (i.e., oil chamber 25 or cylinder 80) to the otherrespective region.

All of the aforementioned throttles 75, 78 may be designed respectivelyas a (local) reduction of a flow cross section. Alternatively, thecorresponding duct may also have a reduced cross section for a (certain)flow length, so that in this way the desired flow rate reduction isaccomplished. While the disclosure has been explained above in regard toan arrangement at the head of the connecting rod, it may be usedaccordingly at the foot of the connecting rod, i.e., at the place wherethe crankshaft is mounted, and this solution is regarded as beingequivalent.

Furthermore, preferably and optionally throttles can be used which areintegrated in the hydraulic system and which limit or reduce the flowrate. These throttles may be arranged directly at the combinedinlet/outlet 16, 18 of the hydraulic drive elements, as is shown by thereference number 78 in FIG. 9. This prevents the system from moving athigh speed and without braking from one end stop against the other endstop. This throttling function or the function of reduction of the flowrate can also be accomplished by suitably dimensioned flow crosssections. A flow cross section reduced for a portion is also possible.Alternatively, a throttle with this function can be arranged at anotherplace, such as adjacent to the check valve 76.

The hydraulic lines as shown in FIG. 11 may be connected to therespective chamber 25 in such a way that they are partly or entirelyclosed by the protrusions 42 shortly before reaching the end positions.The oil passage between the pressurized spaces is increasingly throttledas the end positions are neared. In order to accomplish this, the oilinlet and oil outlet 16, 18 lead radially or at least with a radialdirectional component into the oil chamber 25 and the opening of the oilinlet and oil outlet 16, 18 in an end position of the eccentric lies atleast partly or entirely overlapping with the corresponding protrusion42 of the eccentric 40. When the eccentric 40 nears its end position,the oil volume between the protrusion 42 and the end of the oil chamber25 must thus flow out into the outlet 18, which occurs increasingly witha higher flow resistance on account of the reduced flow cross section,which in turn limits the speed of movement of the eccentric 40.

FIGS. 12 and 13 show a further embodiment of a connecting rod, here withan alternative embodiment of a releasable locking system. FIG. 12 showsa front view, FIG. 13 shows a section along the sectioning line A-Ashown in FIG. 11.

The connecting rod in keeping with the previously representedembodiments comprises a first locking system B1 for the first switchingposition and a second locking system B2 for the second switchingposition. Furthermore, the connecting rod comprises a seat 65. In thisembodiment, the seat 65 is provided for both the locking system B1 andthe locking system B2. That is, in an implementing of the lockingsystems with a pin 62, the pin 62 of the respective locking system B1,B2 engages in the same seat 65. In the exemplary embodiment shown here,this is achieved in that the locking systems B1 and B2 are arranged inthe same plane. FIG. 13 shows the engagement in the second switchingposition, in which the locking system B2 locks the position.Accordingly, in the first switching position with the position of thepin 62 locked, the locking system B1 engages with the seat 65 (notshown). The benefit of this embodiment is that only one seat needs to beprovided. This enables more economical manufacturing and/or benefits interms of strength.

FIGS. 14 to 16 show a further embodiment of a connecting rod, here witha further alternative embodiment of a releasable locking system. FIG. 14shows a front view, FIGS. 15 and 16 show a section along the sectioningline A-A shown in FIG. 14.

The connecting rod in keeping with the previously representedembodiments comprises a first locking system B1 for the first switchingposition (FIG. 15) and a second locking system B2 for the secondswitching position (FIG. 16). Furthermore, the connecting rod comprisestwo seats 65. One seat is associated respectively with one of the twolocking systems.

In this embodiment, the pin 62 of the locking systems B1, B2 is situatedrotated by an angle α with respect to the eccentric axis. This makes itpossible to ensure a faster and more reliable unlocking by oil pressure.A rotation in the range of 5°-15° has been found to be especiallyadvantageous. In this exemplary embodiment, the rotation is α=10°.

A further variant (not shown) calls for providing a seat 65 for bothlocking systems B1 and B2 and for the pins of the locking system to berotated with respect to the eccentric axis.

Although the disclosure has been explained above in regard to anarrangement at the head of the connecting rod, it can also be usedaccordingly at the foot of the connecting rod, i.e., at the placemounted on the crankshaft, and this solution is regarded as beingequivalent.

1. An internal combustion engine having a connecting rod with a devicefor changing a compression ratio (VCR) of the internal combustionengine, the internal combustion engine comprising: a connecting rod headand a connecting rod pin which is mounted by an eccentric relative tothe connecting rod head, wherein: either the connecting rod head or theconnecting rod pin comprises at least one oil chamber and the eccentriccomprises a protrusion reaching into the oil chamber, or the eccentriccomprises or delimits at least one oil chamber and the connecting rodhead or the eccentric comprises a protrusion reaching into the oilchamber, such that an oil pressure in the oil chamber exerts a force onthe protrusion to change the eccentric setting of the eccentric.
 2. Theinternal combustion engine according to claim 1, wherein the oil chamberhas a defined movement range (a) for the protrusion, at the ends ofwhich is situated respectively an oil inlet and an oil outlet and theangle range (a) is preferably limited by end stops.
 3. The internalcombustion engine according to claim 1, wherein the eccentric isadjustable with respect to the connecting rod head in an angle range (a)and the eccentric comprises between the connecting rod head and theeccentric a lubricant supply chamber and the eccentric comprises abreach associated with the lubricant supply chamber, so that regardlessof a set angle of the angle range (a) a fluidic connection always existsbetween a supply duct of the connecting rod and a supply duct of theconnecting rod pin.
 4. The internal combustion engine according to claim1, wherein a lubricant supply chamber is provided in a plane in whichthe oil chamber is also provided.
 5. The internal combustion engineaccording to claim 1, wherein a lubricant supply chamber is provided ina plane in which the oil chamber is not situated.
 6. The internalcombustion engine according to claim 1, wherein the connecting rodcomprises at least two oil chambers, each one having a protrusion. 7.The internal combustion engine according to claim 1, wherein theconnecting rod head further comprises: a locking, which is hydraulicallyactuable, and which can be brought into a state of locking whichprevents a relative movement of the connecting rod head and theeccentric which prevents a relative movement of the eccentric and theconnecting rod pin.
 8. The internal combustion engine according to claim1, wherein the oil chamber or oil chambers further comprises: an oilinlet and an oil outlet at opposite ends in order to realize a firstcompression ratio, whose functions can be exchanged in order to realizea second compression ratio.
 9. The internal combustion engine accordingto claim 1, wherein the eccentric can be adjusted in an angle range (a)of more than 40° and in an angle range (a) less than 160°.
 10. Theinternal combustion engine according to claim 1, wherein the eccentricis adjustable in an angle range (a) of less than 120°.
 11. The internalcombustion engine according to claim 1, wherein: a releasable locking isprovided in at least one switching position, wherein the locking in thelocking position prevents in particular a rotating of the eccentricrelative to the connecting rod head.
 12. The internal combustion engineaccording to claim 11, wherein a releasable locking is provided in eachcase in at least two switching positions.
 13. The internal combustionengine according to claim 11, wherein the locking comprises a pin, whichcan engage with a seat, and a hydraulic drive is provided in particularfor this.
 14. The internal combustion engine according to claim 11,wherein the connecting rod comprises at least one and preferably twohydraulic drives each with a hydraulic piston and a hydraulic cylinderfor adjusting the eccentric setting.
 15. The internal combustion engineaccording to claim 11, wherein: a drain from the hydraulic system of theconnecting rod, the drain having a relief throttle, is provided, bywhich system hydraulic fluid can be supplied to the engine interiorafter the activation of a switching actuator for the switching process,wherein the relief throttle may also be designed as a duct with areduced cross section and in particular the reduced cross section ofthis duct is less than 25% of the duct for the supply of the hydraulicfluid for the compression change.
 16. The internal combustion engineaccording to claim 11, wherein: a drain from the hydraulic system of theconnecting rod, the drain having a relief throttle, is provided, bywhich system hydraulic fluid can be supplied to the engine interiorafter the activation of a switching actuator for the switching process,and the relief throttle is arranged in a valve, especially the switchingactuator, and in particular the relief throttle is designed as a leakageof a valve and/or a hydraulic element, such as preferably the oilchamber.
 17. The internal combustion engine according to claim 15,wherein no hydraulic fluid is supplied via the relief throttle to theengine interior in the time span after performing a switching of thecompression ratio until a new activation of the switching actuatoroccurs.
 18. An internal combustion engine having a connecting rod with adevice for changing a compression ratio (VCR) of the internal combustionengine, the internal combustion engine comprising: a connecting rod headand a connecting rod pin, which is mounted by an eccentric relative tothe connecting rod head, wherein two end positions are provided for theadjustability of the eccentric and a dampening is provided for at leastone end position in that a component, preferably a protrusion of theeccentric, reduces a flow channel for a hydraulic fluid inposition-dependent manner, in order to thereby reduce the velocity ofthe eccentric during the movement into an end position.
 19. An internalcombustion engine having a connecting rod with a device for changing acompression ratio (VCR) of the internal combustion engine, the internalcombustion engine comprising: a bearing region for mounting theconnecting rod relative to a piston and a bearing region for mountingthe connecting rod on a crankshaft of the internal combustion engine,wherein a switching actuator for activating the adjustment of thecompression ratio is arranged between the two bearing regions.
 20. Theinternal combustion engine according to claim 19, further comprising: areleasable locking is provided in each case in at least two switchingpositions; a first pin; a second pin; and a seat, wherein the connectingrod is configured such that in the first switching position the firstpin can engage with the seat and in the second switching position thesecond pin can engage with the seat.